1. Field of the Invention
The present invention relates to a liquid discharge recording head for applying a plurality of different types of liquids such as ink of a plurality of colors to paper or other record mediums and a liquid discharge recording apparatus with the liquid discharge recording head mounted thereon for printing.
2. Related Background Art
A printer, particularly an ink-jet recording type printer is capable of outputting high-quality characters or images at low cost, thus rapidly spreading in office or home applications. Some products enable a black-character quality, a density, and a water resistance equivalent to those of commercial prints in text outputs. As far as images, there appeared products realizing colors and gradations equivalent to a silver gelatin (salt) print. In future, a lower cost and a high-speed output will be demanded as well as the above performances.
Referring to FIG. 19, there is shown a perspective view partially exploded for an explanation of a configuration of a general color-ink-jet recording head. A base 218 has three through holes (liquid supplying apertures) 219 formed thereon, to which ink of cyan, magenta, and yellow is supplied. The top surface of the base is covered with a nozzle formation member 223, in which ink flow path strings are formed in contact with respective through holes 219, electrical heat converting elements 220 are formed at the bottoms of the ink flow paths on the top surface of the base, and further orifices 224 are formed correspondingly to the electrical heat converting elements. In color recording by using an ink-jet recording head having this base, the head scans a record medium concurrently with attaching ink to the record medium in an order of cyan, magenta, and yellow and an image is formed by repeating this operation. While the head moves backward on the record medium, discharging in the arrangement order causes the order of colors to be reversed on the record medium and results in a hue change, thereby causing color-shading. Although it can be prevented by separating the arrangement order from the discharging order, it is not advantageous in high-speed recording. In addition, while it is necessary to increase a record frequency by increasing the number of orifices for high-speed recording, it increases an ink flow rate per unit time in the inside of the through hole and a pressure fluctuation in the inside thereof, thus giving unfavorable vibrations to a meniscus at the orifice. Particularly to increase the discharge frequency, there is a method of decreasing a flow path resistance, for example, by shortening the flow path to increase an ink moving speed in the ink flow path, while it also causes the vibrations of the meniscus at the orifice to be more sensitive to a pressure fluctuation inside the through hole. This problem will be serious in an area having a small droplet quantity of 10 pl (picoliters, 10 to 12 liters) or lower.
In view of these problems, it is a primary object of the present invention to provide a recording head capable of providing high-speed color reciprocating printing free from color-shading in the minimum base size, wherein the recording head is a liquid discharge recording head capable of maintaining a high-quality image by attenuating a pressure fluctuation inside the liquid supplying aperture at the liquid discharge and to provide a liquid discharge recording apparatus having the recording head.
According to one aspect, the present invention which achieves these objects related to a liquid discharge recording head comprising a plurality of orifice strings each having a plurality of orifices arranged correspondingly to respective recording liquids for discharging recording liquids of a plurality of colors, a plurality of liquid flow paths and electrical heat converting elements corresponding to the plurality of orifices, and a plurality of liquid supplying apertures arranged along the orifice strings for supplying the recording liquids of the plurality of colors in the plurality of liquid flow paths, wherein each of the orifice strings corresponding to the recording liquids of the plurality of colors is symmetrically arranged about a head scanning direction regarding the same color of the recording liquid and the head has a plurality of chambers having communication with the liquid flow paths in the opposite side of the orifice strings with the liquid supplying apertures therebetween. According to this arrangement, the color order for implanting droplets in a record medium is the same for recording in both forward and backward direction, thereby preventing color-shading and reducing a pressure fluctuation inside the through holes effectively, by which high-speed bidirectional recording can be performed.
The above recording head preferably has an odd number of the liquid supplying apertures and an even number of the orifice strings, with the middle liquid supplying aperture among the plurality of liquid supplying apertures disposed between the orifices, the electrical heat converting elements, and the liquid flow paths and with other liquid supplying apertures having orifices, electrical heat converting elements, and liquid flow paths in a single side of the other liquid supplying apertures.
In this condition, the orifice strings (lines), the electrical heat converting elements, and the liquid flow paths are disposed almost line-symmetrically about the middle liquid supplying apertures.
In this manner, by disposing the liquid supplying apertures other than the middle one among the plurality of liquid supplying apertures for supplying liquids to the plurality of liquid flow path strings (lines), the orifice strings, the heat resistance elements, the liquid flow paths, and driver circuits so as to have line symmetry about the middle ink supplying apertures, the liquid supplying apertures and the driver circuits can be disposed at regular intervals on the base efficiently, thus minimizing the base size. The reduction of the base size decreases a capacity of a memory for retaining transfer data to the recording head proportionally to the base size, thus enabling the cost to be lowered.
Furthermore, in the above recording head, preferably the ith orifices counted from each end of the orifice strings belonging to a left half or a right half of the middle liquid supplying apertures are disposed on a single line and the ith orifice in the left half and the ith orifice in the right half are disposed with a difference by a half pitch in the column direction. This enables printing of high precision and fineness which is substantially twice those of the orifice array pitch.
Particularly, in the above liquid discharge recording head, the present invention comprises a plurality of chambers (hereinafter, referred to as buffer chambers) having communication with the liquid flow paths in the opposite side of the orifices about the liquid supplying apertures on the same plane as for the liquid flow paths in contact with the liquid supplying apertures. According to this arrangement, an air easily remains in the buffer chambers even in a condition in which the liquid supplying apertures and the liquid flow paths are filled with liquids, thereby enabling an attenuation of pressure fluctuations inside the liquid supplying apertures caused by discharging droplets. This reduces a meniscus vibration at driving a discharge, thereby enabling a high-quality image to be maintained.
In this recording head, the number of the buffer chambers is preferably the same as the number of the liquid flow paths. In addition, preferably a pitch of the buffer chambers adjacent to each other is the same as a pitch of the liquid flow paths adjacent to each other and the buffer chambers are opposite to the liquid flow paths and disposed with a half-pitch difference relative to the liquid flow paths. A shape of the buffer chamber is preferably almost the same as that of the liquid flow path.
Furthermore, in the above head, preferably there are at least three colors of cyan, magenta, and yellow for the plurality of liquid colors with the yellow ink supplied to the middle liquid supplying aperture among the plurality of liquid supplying apertures.
The buffer chambers may have communication with the liquid supplying apertures other than the middle liquid supplying aperture. In addition, the buffer chambers may form grooves each having a desired shape in a portion in contact with the middle liquid supplying aperture of a member forming the liquid flow paths and may be formed by covering these grooves with a thin film member.
Furthermore, the liquid flow paths and the buffer chambers may be formed by coating the base with a positive photosensitive resin, exposing and developing it to shapes of molds of the liquid flow paths and the buffer chambers, coating it with a negative photosensitive resin, and then removing the positive photosensitive resin.
In addition, the present invention includes a liquid discharge recording apparatus, which has a carriage for detachably mounting the liquid discharge recording head, for recording on a record medium by discharging droplets from a desired orifice string of the liquid discharge recording head with a scanning of the carriage.